This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. ABSTRACT Thromboembolism, often under-recognized in children, has significant consequences with regards to morbidity and mortality. While some patients have severe manifestations (i.e. pulmonary embolism, superior vena cava syndrome, cerebrovascular events), others exhibit few of these clinical symptoms. The underlying mechanism affecting this variability has been poorly characterized, as there is no clear correlation between current diagnostic evaluations and prothrombotic potential. Currently, in the absence of contraindications, the treatment for pediatric thromboembolism includes the use of anticoagulation. The paucity of prospective pediatric clinical trials data evaluating therapy, recurrence, and long-term complications has impacted the care of these patients. Out of necessity, the current standard of care has been extrapolated from the adult experience. Furthermore, there are limited options for predicting post-thrombotic complications (i.e. progression, recurrence, and/or post-thrombotic syndrome). The purpose of this protocol is to establish a patient registry through which a common set of data are collected from patients with thromboses at Texas Children''s Hospital to gain a better understanding of the pathophysiology of thrombosis, the current clinical management of patients with thromboses, the safety and efficacy of treatments, and post-therapy outcomes. I. HYPOTHESIS This is a database study to evaluate anticoagulation therapy and the natural history of thrombotic disorders in neonates and children. We hypothesize that evaluation of the diagnoses of thrombosis and clinically collected treatment data will enable us to improve our current therapy for these disorders. II. SPECIFIC AIMS The purpose of this protocol is to establish a patient registry through which a common set of data are collected from patients with thromboses at Texas Children''s Hospital to gain a better understanding of the pathophysiology of thrombosis, the current clinical management of patients with thromboses, the safety and efficacy of treatments, and post-therapy outcomes. The TCH Registry will be a data repository in which patient socio-demographic, clinical, and quality of life data are stored. The objectives of this protocol include: 1. To provide insight into the variation in the management of thrombotic disorders and the association between particular patterns of practice and patient outcomes. 2. To gain further insight into the natural history of patients with thrombotic disorders and the safety and effectiveness of current therapies.